Quick disconnect system for coupling a golf club head with a golf club shaft

ABSTRACT

A hosel fitting for connecting a shaft to one of a plurality of club heads comprises a first portion of a tubular structure configured to be affixed to the end of the shaft and a second portion of the tubular structure configured to be received by a bore in a club head. The second portion of the tubular portion can be configured to extend down into the bore. The hosel fitting can also comprise a fastener receiving portion for receiving a fastener configured to affix the hosel fitting to any one of the plurality of club heads.

RELATED APPLICATIONS INFORMATION

This application claims priority as a Continuation under 35 U.S.C. §120to U.S. application Ser. No. 10/053,797, entitled “Golf Club Woods WithWood Club Head Having A Selectable Center of Gravity and a SelectableShaft,” filed Jan. 18, 2002, which is incorporated herein by referenceas if set forth in full.

BACKGROUND

1. Field

This invention relates to wood golf clubs and, more particularly, tosuch wood golf clubs wherein the vertical center of gravity of the woodclub head is selectable.

2. Background

The golf clubs that are used to hit the golf ball the greatest distancesare the “woods”. The woods originally were made of natural wood buttoday are made of metals or composite materials. However, they continueto be termed “wood golf clubs” or “woods”, and that terminology is usedherein.

The wood golf clubs have wood club heads with relatively large mass, andloft angles of the faces relative to the soles selected to achieve along flight distance of the struck golf ball. A golf player typicallycarries up to five woods, which are distinct from each other in that theloft angle varies from about 7 to about 11 degrees for a driver woodgolf club, and about 12 degrees and higher for other wood golf clubs. Ofthe golf clubs termed “woods”, the drivers, with relatively low loftangles, are designed to hit the golf ball the greatest distances. Thegolfer selects the required wood golf club from this group of wood golfclubs. A wood golf club, and normally a driver, is used for most longshots from the tee, and may be used on intermediate shots on some longerholes.

As the game of golf has been studied analytically, it has become clearthat the design of the wood golf club plays a part in the ability of theplayer to hit long, accurately directed shots. For example, the shapesof the wood club heads have been optimized. Large-sized wood club headshave been introduced. Wood club heads have been designed to allow theplayer to add weight to the wood club head.

While these approaches yield benefits, the present inventors haveobserved that most players still cannot obtain wood golf clubs that areoptimal for the individual. Players vary according to weight, height,strength, skill and other factors. Wood golf clubs may be purchased withvarying shaft lengths, but the wood club heads themselves do not change,except as to the loft angle of the face and the ability to add weight tothe wood club head in some designs. These approaches do not provide therequired flexibility in selecting the wood club heads that are bestsuited to the individual player.

There is a need for an improved approach to the design of wood clubheads, which allows the player to obtain wood golf clubs that areoptimized for the individual. The present invention fulfills this need,and further provides related advantages.

SUMMARY

A hosel fitting for connecting a shaft to one of a plurality of clubheads comprises a first portion of a tubular structure configured to beaffixed to the end of the shaft and a second portion of the tubularstructure configured to be received by a bore in a club head. The secondportion of the tubular portion can be configured to extend down into thebore. The hosel fitting can also comprise a fastener receiving portionfor receiving a fastener configured to affix the hosel fitting to anyone of the plurality of club heads.

In one aspect, the bore, hosel fitting, and shaft are alwayssubstantially in line. In other words, the purpose of the hosel fittingis not to realign the angel of the shaft the club head, i.e., it is notintended to adjust the lie angel. Rather, the hosel fitting is meant toallow anyone of a plurality of shafts to be interfaced with a club head,so that differnet shaft configurations can be tested without changingany other parameters.

Other features and advantages of the present invention will be apparentfrom the following more detailed description of the preferredembodiment, taken in conjunction with the accompanying drawings, whichillustrate, by way of example, the principles of the invention. Thescope of the invention is not, however, limited to this preferredembodiment.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a wood golf club according to theinvention;

FIGS. 2-4 are sectional views taken on line 2-2 of FIG. 1, illustratinga preferred technique for adjusting the center of gravity of the woodclub head;

FIGS. 5-7 are side sectional views, like those of FIGS. 2-4, and takenon line 2-2 of FIG. 1, illustrating a second technique for adjusting thecenter of gravity of the wood club head;

FIG. 8 is an enlarged, partially exploded, sectional view of the woodclub head, taken on line 8-8 of FIG. 1; and

FIG. 9 is a block diagram of a method of providing a wood golf club fora player.

DETAILED DESCRIPTION

FIG. 1 depicts a wood golf club 20. The wood golf club 20 is sometimestermed a “wood” club or a “wood”. The wood golf club 20 includes a woodclub head 22 and a generally cylindrical wood club shaft 24 affixed tothe wood club head 22. The wood club shaft 24 may be of any operablematerial of construction, such as metal (e.g., titanium, aluminum),composite (e.g., graphite/epoxy), or even natural wood; produced by anyoperable method; of any operable diameter; of any operable length; andof any operable physical properties (e.g., elastic modulus, strength).One of the features of the present invention, as will be discussedsubsequently in relation to FIG. 8, is that the wood club shaft 24 isreadily interchangeable.

FIG. 2 is a sectional view through the wood club head 22. In thepreferred form, the basic structure of the wood club head 22 preferablyincludes two pieces, a one-piece wood head body 26 and a one-piece woodhead face plate 28 affixed to the wood head body 26 by a weldment 30, byan adhesive, or by other means for affixing. The wood head body 26 maybe described in terms of two regions pertinent to the presentdiscussion, a generally planar sole 32 that rests upon the ground 34,and a crown 36 that is visible to the eye of the player when the playerholds the wood golf club 20 and looks downwardly toward the wood clubhead 22. The wood head body 26 is preferably hollow, and the crown 36 isconvexly (outwardly) curved relative to the interior of the wood headbody 26. The crown 36 is the convexly, outwardly curved portion of thewood head body 26 that is uppermost in FIG. 2. The sole 32 is thelowermost portion of the wood head body 26 in FIG. 2, which is flat overmost of its area and slightly upwardly curved toward the left hand sideof FIG. 2 (remote from the wood head face plate 28). The sole 32 meetsand is contiguous with the crown 36 on the left hand side of FIG. 2.

The wood head body 26 may be made of any operable material, but ispreferably made of a metal alloy such as a titanium alloy. The wood headbody 26 may be made by any operable manufacturing process, but ispreferably made by a casting technique such as lost wax casting or diecasting. It may also be forged or machined. The wood head face plate 28is made separately from the wood head body 26. The wood head face plate28 is preferably also a metal alloy such as a titanium alloy, but adifferent alloy composition than used in the wood head body 26. The woodhead face plate 28 is preferably forged. After the wood head body 26 andthe wood head face plate 28 are fabricated separately, they are joinedby fitting the wood head face plate 28 into a recess formed on the woodhead body 26 and then welded, adhesively bonded, or otherwise attachedin place by the weldment 30 that extends around the periphery of thewood head face plate 28.

The inventors have determined that an important performancecharacteristic of the wood golf club 20 is a vertical location of acenter of gravity 38 of the wood head body 26. The “vertical location”is a distance D_(CG) from an external surface 40 of the sole 32 towardthe crown 36 measured along a line 42 perpendicular to the planarportion of the sole 32.

FIGS. 2-4 illustrate three wood club heads 22 for a set of wood golfclubs 20. These three wood club heads 22 of FIGS. 2-4 have substantiallythe same external shapes and volumes. The three wood club heads 22 alsohave substantially the same total weights. The shapes, volumes, andweights of the three wood club heads 22 in this set of wood golf clubs20 are substantially the same in order to allow optimization of theselection of the vertical location of the center of gravity 38, withoutsimultaneously varying other parameters such as shape, loft angle, andtotal weight of the wood club head 22.

The vertical locating of the center of gravity 38 of the three wood clubheads 22, while maintaining the limitation of substantially constantexternal shape, volume, and total weight, may be accomplished by anyoperable approach. FIGS. 2-4 illustrate a preferred approach, changingthe thicknesses of the sole 32 and the crown 36 to redistribute weightand move the center of gravity 38 vertically. The thickness changes andthe movement of the center of gravity 38 are quite small and may bedifficult to discern in precisely scaled drawings, so in FIGS. 2-4 thethickness variations and the vertical displacement of the center ofgravity 38 are exaggerated. In the wood club head 22 of FIG. 2, athickness t_(s) of the sole 32 is relatively large, and a thicknesst_(c) of the crown 36 is relatively small, so that the weight of thesole is relatively large and the weight of the crown is relativelysmall. Consequently, the center of gravity 38 is relatively low (i.e.,near to the sole 32). (The exact locations where the thickness of thesole and the thickness of the crown are measured is not critical, aslong as they are generally in the centers of the respective regions andare consistently positioned from wood club head to wood club head withina set.) The weight of a region such as the crown or the sole generallycorrelates with its thickness within this set of club heads, so that thethicker the region, the greater its weight. In the wood club head 22 ofFIG. 3, the thickness t_(s) of the sole 32 is smaller than that of thewood club head 22 of FIG. 2, and the thickness t_(c) of the crown 36 isgreater than that of the wood club head 22 of FIG. 2. The result is thatthe center of gravity 38 of the wood club head 22 of FIG. 3 is higher(i.e., further from the sole 32) than the center of gravity 38 of thewood club head 22 of FIG. 2. In the wood club head 22 of FIG. 4, thethickness t_(s) of the sole 32 is smaller than that of the wood clubhead 22 of FIG. 3, and the thickness t_(c) of the crown 36 is greaterthan that of the wood club head 22 of FIG. 3. The result is that thecenter of gravity 38 of the wood club head 22 of FIG. 4 is higher (i.e.,further from the sole 32) than the center of gravity 38 of the wood clubhead 22 of FIG. 3. The wood club head 22 of FIG. 2 is termed the “L”(low) center of gravity variation, the wood club head 22 of FIG. 3 istermed the “M” (medium) center of gravity variation, and the wood clubhead 22 of FIG. 4 is termed the “H” (high) center of gravity variation.More variations in the vertical location of the center of gravity 38 maybe provided than the three illustrated, but initial testing indicatesthat three variations are sufficient for most applications. The changesin thickness of the sole 32 and of the crown 36 in each case areselected so that the total weight of the wood club head 22 remains thesame. The changes in thickness are accommodated by varying the positionof an inner wall 44 of the wood club head 22, so that the shape of anouter wall 46 remains unchanging.

The wood head bodies 22 of FIGS. 2-4 are preferably manufactured by alost wax casting approach. This technique is known generally for themanufacture of hollow golf club head bodies of other designs, see forexample U.S. Pat. No. 5,429,365. Generally, there is an outer castingshell that defines the position, shape, and size of the outer wall 46,and a casting core that defines the position, shape, and size of theinner wall 44. In the present case, the outer casting shell used for thethree wood club heads 22 of FIGS. 2-4 is the same, so that the wood headbodies 22 have the same external shape, loft angle, and volume, about335 cubic centimeters in the preferred approach. The casting cores usedto cast the three wood head bodies 26 have a constant volume, so thatthe total amount of metal (and thence the weight) in each of the woodhead bodies 26 is a constant amount, preferably in the range of fromabout 195 to about 205 grams in the preferred approach wherein the woodhead bodies 26 are cast from the titanium alloy titanium-6 weightpercent aluminum-4 weight percent vanadium. The casting cores aredifferently positioned, so as to define the thicknesses of the sole 32and the crown 36 in the manner discussed previously to produce the threedifferent types of wood club heads 22 of FIGS. 2-4.

Once the outer casting shell and the casting core are positioned, moltenmetal is poured into the space therebetween and cooled to solidify andto form each of the wood head bodies 22. Any operable castable materialmay be used, but a titanium alloy such as titanium-6 weight percentaluminum-4 weight percent vanadium is preferred. After the cast metalhas solidified, the outer casting shell and the casting core areremoved, leaving the final hollow cast wood club head 22 having a castmicrostructure. In alternative fabrication techniques, such as a forgedor a machined microstructure, the final wood club head 22 has acorresponding microstructure such as a forged or a machinedmicrostructure, respectively.

Other operable techniques for changing the vertical location of thecenter of gravity 38 may be used, and FIGS. 5-7 illustrate one suchalternative approach. The pertinent parts of the prior discussion of theembodiments of FIGS. 2-4 are incorporated here. In the embodiment ofFIGS. 5-7, a sole fitting 48 is formed in the sole 32, and a crownfitting 50 is formed in the crown 36. These fittings 48 and 50 areexternally accessible. A corresponding sole weight insert 52 and a crownweight insert 54 are inserted into the respective sole fitting 48 andcrown fitting 50. In a preferred version of this embodiment, thefittings 48 and 50 are female-threaded fittings, and the weight inserts52 and 54 are matching male-threaded weights. The weight inserts 52 and54 may be readily installed, removed, and moved in various combinations.The total weight of the sole weight insert 52 and the crown weightinsert 54 is maintained constant, so that the total weight of the woodclub heads 22 of FIGS. 5-7 remains constant.

The approach of FIGS. 2-4 has the advantage that the weight change isdistributed broadly over the sole and the crown. The approach of FIGS.5-7 has the advantage that the weight inserts 52 and 54 may be readilychanged. The approach of FIGS. 5-7 has the additional advantage that thetotal of the weight inserts 52 and 54 may be readily changed, ifdesired.

The wood club heads of FIGS. 2-4 and 5-7 are illustrated as beingconventional in configuration, except for the ability to change thevertical location of the center of gravity. Other modifications thathave been found or may be found useful in wood club heads, such aschanges in external shape or total weight, or material of construction,may be utilized in conjunction with the present approach.

The approaches of FIGS. 2-4 and FIGS. 5-7 are used to change thevertical location of the center of gravity 38. Another factor thatsignificantly influences the performance of the wood golf club 20 is thenature of the wood club shaft 24. FIG. 8 illustrates an embodiment ofthe present approach that allows various types of wood club shafts 24 tobe used with the variations of FIGS. 2-4 and FIGS. 5-7. The preferredwood club head 22 of the present approach has no integral hosel, whichis a tubular portion that extends upwardly from the crown 36 of theconventional wood club head. The wood club shaft of the conventionalwood club is inserted into the hosel and affixed to the hosel with anadhesive such as an epoxy.

In the present approach as seen in FIG. 8, the wood club head 22 has nohosel, but instead has a bore 60 fabricated into the wood head body 26.The bore 60 has a base 62 that defines the bottom of the bore 60. Anaperture 64 extends through the base 62. The bore 60 is sized to receivea hosel fitting 66 affixed to an end 68 of the wood club shaft 24. (Thehosel fitting 66 is not integral with the wood club head 22.) The bore60 is oriented in the wood club head 22 so that the wood club shaft 24has the proper orientation to the wood club head 22 and to the wood headface plate 28. A fastener, preferably a male-threaded fastener 70 suchas the illustrated bolt, extends through the aperture 64 of the base 62to engage the female-threaded hosel fitting 66, and thence the wood clubshaft 24, to the respective wood club head 22, when the hosel fitting 66is inserted into the bore 60. The sole 32 is locally recessed at recess72 so that the head of the fastener 70 does not strike the ground 34when the wood golf club 20 is swung. With this approach, the wood clubshaft 24 may be readily changed so that different shafts may be testedand possibly used with the various wood club heads 22. Shafts ofdifferent lengths, diameters, materials of constructions, elasticproperties, and other characteristics may thence be utilized.

An important application of the present approach is to maximize theperformance of the golf player for the wood golf clubs, by providing theoptimal wood golf club equipment for the individual player. FIG. 9illustrates this approach. A wood golf club of a test configuration isprovided, numeral 80. The performance of the wood golf club testconfiguration when used by the particular player is analyzed, numeral82. The steps 80, 82 are repeated, numeral 84, for a new testconfiguration, and may be repeated as many times as necessary todetermine the optimum performance of the player as a function of theseveral variables that may be evaluated. Variables that may be includedin the evaluation include the wood club head 22 and particularly thevertical location of the center of gravity of the wood club head, asdiscussed above, the type of drive club shaft 24 that is installed tothe wood club head 22, and the type of golf ball being hit. Thisprocedure would be used for a first set of wood golf clubs with aconstant selected loft angle, and then may be used for additional setsof wood golf clubs with a different (but constant within any one set)loft angle. The present procedure is expected to yield the most benefitsfor the wood golf clubs with the lowest loft angles, termed the“drivers”, but it may be used as well for other wood golf clubs.

The following performance tables for golfers A, B and C, employees ofthe assignee, were developed by the procedure of FIG. 9 during theinitial testing of the present approach. Each entry in the tablesrepresents the average of multiple hits of a single commercial brand ofgolf ball. Performance was evaluated using a standard Launch Monitordevice for analyzing golf ball movement. In each case, the golfer usedthree wood golf clubs 20. The wood club head 22 in each case was a 335cubic centimeter, 200 gram, 7.5 degree loft angle club. The variationbetween the wood golf clubs was a low (L), medium (M), or high (H)vertical position of the center of gravity 38. The following table givesthe approximate thicknesses, measured in inches, of the sole 32 and thecrown 36 at the same respective point on each wood club head, and theresulting vertical position of the center of gravity in millimeters.Club Ident. Sole Thickness Crown Thickness Center of Gravity H 0.0400.060 32 M 0.050 0.050 30 L 0.060 0.040 28

In the following performance tables, the table entries are, from left toright, the wood club head identification (L, M, or H), the initiallaunch speed (Vo) of the ball in miles per hour, the spin rate (SR) ofthe ball in revolutions per minute, the launch angle (LA) of the ball indegrees, the carry distance (CD) on the fly of the golf ball in yards,and the total distance (TD) of the golf ball on the fly and rolling, inyards. Golfer A Club Ident Vo SR LA CD TD H 160.5 2066 8.6 228.7 265.4 M160.3 2163 9.4 237.9 268.2 L 161.2 2436 9.7 239.0 271.9

Golfer B Club Ident Vo SR LA CD TD H 158.9 1992 9.9 229.8 266.2 M 158.82263 10.0 233.7 267.8 L 159.7 2745 10.2 240.5 271.1

Golfer C Club Ident Vo SR LA CD TD H 161.4 3169 14.8 250.9 276.7 M 159.53400 15.3 247.8 272.2 L 160.1 3384 16.3 248.7 272.8

The results set forth in these tables are not to be interpreted as goodor bad, consistent or inconsistent. These results simply reflect theperformance of each individual player using various types of wood clubcombinations and for a single type of golf ball.

In these data, Golfers A and B each achieves the greatest carry distanceand total distance with the low center of gravity wood club head. GolferC, on the other hand, achieves the greatest carry distance and totaldistance with the high center of gravity wood club head. Based on thisdata, the selection of wood club heads for Golfers A and B would bedifferent than for Golfer C. These extremely limited data are presentedto illustrate the operation of the present approach. In practice, muchmore data would be gathered for each player, including the effects ofvariations in the shape and volume of the wood club head, the weight ofthe wood club head, the loft angle of the wood club head, the type ofwood club shaft, the materials of construction of the wood club shaftand the wood club head, the golf ball played, and even other featuresavailable in wood club heads.

This approach may be used in a custom-fitting procedure to find a singlewood golf club that is optimal for that player, taking into account allof the variables discussed above. Once that single wood golf club isidentified, then the illustrated version with the removable shaft (FIG.8) may be used by the player. To make the illustrated embodiment into apermanent wood golf club, the hosel fitting 66 may be fixed in placewith a permanent adhesive, and a cap may be fitted over the head of thefastener 70 and fixed in place with the permanent adhesive. In othercases, other variables may be considered: wind conditions, launch angle,heel/toe properties, side spin, accuracy relative to an axis, distanceaccuracy, face mapping, and the like. Thus, for example, a number ofgolf clubs may be identified for use by the player, such as a wood golfclub driver for use in still air conditions, a wood golf club driver foruse in headwinds, a wood golf club driver for use in tailwinds, and thelike.

Although a particular embodiment of the invention has been described indetail for purposes of illustration, various modifications andenhancements may be made without departing from the spirit and scope ofthe invention. Accordingly, the invention is not to be limited except asby the appended claims.

1. A hosel fitting for connecting a shaft to one of a plurality of clubheads comprising: a first portion of a tubular structure configured tobe affixed to the end of the shaft; a second portion of the tubularstructure configured to be received by a bore in a club head, the secondportion of the tubular portion extending downwardly into the bore; afastener receiving portion for receiving a fastener configured to affixthe hosel fitting to any one of the plurality of club heads; and whereinthe bore, hosel fitting, and shaft are always substantially in line. 2.The hosel fitting of claim 1, wherein the fastener receiving portioncomprises a female-threaded fastener receiver configured to receive amale-threaded fastener.
 3. The hosel fitting of claim 2, wherein themale-threaded fastener comprises a bolt.
 4. The hosel fitting of claim1, wherein the fastener receiving portion comprises a male-threadedfastener receiver configured to receive a female-threaded fastener. 5.The hosel fitting of claim 1, wherein the second portion of the tubularstructure is configured to extend downwardly into the bore until itcontacts a base of the bore.
 6. A golf club assembly, comprising: afastener; a club head comprising a bore; a shaft; and a hosel fittingfor connecting the shaft to the club head, the hosel fitting having: afirst portion of a tubular structure configured to be affixed to the endof the shaft; a second portion of the tubular structure configured to bereceived by the bore in the club head, the second portion of the tubularportion extending downwardly into the bore; a fastener receiving portionfor receiving the fastener, the fastener configured to affix the hoselfitting the club head, wherein the bore, hosel fitting, and shaft arealways substantially in line.
 7. The golf club assembly of claim 6,wherein the fastener receiving portion comprises a female-threadedfastener receiver, and wherein the fastener is a male-threaded fastener.8. The golf club assembly of claim 7, wherein the male-threaded fastenercomprises a bolt.
 9. The golf club assembly of claim 6, wherein thefastener receiving portion comprises a male-threaded fastener receiver,and wherein the fastener comprises a female-threaded fastener.
 10. Thegolf club assembly of claim 6, wherein the bore comprises a base, andwherein the second portion of the tubular structure is configured toextend downwardly into the bore until it contacts the base of the bore.11. The golf club assembly of claim 10, wherein the bore furthercomprises an aperture in the base, wherein the fastener is configured toextend through the aperture to mate with the fastener receiving portion.12. The golf club assembly of claim 6, wherein the bore is configured toorient the shaft properly when the shaft is connected to the club headusing the hosel fitting.
 13. The golf club assembly of claim 6, whereinthe fastener is configured to allow the club head to be exchange with adiffernet club head.
 14. The golf club assembly of claim 13, wherein thedifferent club head comprises a different center of gravity relative tothe first club head.
 15. The golf cub assembly, wherein the fastenerallows the shaft to be exchange with a different shaft.
 16. The golfclub assembly of claim 6, wherein the club head comprises a recesssubstantially below the bore, the recess configured so that the fastenerwill not strike the ground when the golf club assembly is swung.
 17. Thegolf club assembly of claim 6, wherein the golf club head is a wood typegolf club head.
 18. The golf club assembly of claim 6, wherein the golfclub head is an iron type golf club head.
 19. The golf club assembly ofclaim 6, wherein the golf club head is a hybrid type golf club head. 20.A system for fitting a golfer fro a golf club, comprising: at least oneclub head comprising a bore; a fastener; and at least one shaft assemblycomprising a shaft and a hosel fitting, the hosel fitting comprising: afirst portion of a tubular structure configured to be affixed to the endof the shaft; a second portion of the tubular structure configured to bereceived by the bore in the club head, the second portion of the tubularportion extending downwardly into the bore; a fastener receiving portionfor receiving the fastener, the fastener configured to affix the hoselfitting club head, wherein the bore, hosel fitting, and shaft are alwayssubstantially in line.
 21. The system of claim 20, wherein the fastenerreceiving portion comprises a female-threaded fastener receiver, andwherein the fastener is a male-threaded fastener.
 22. The system ofclaim 21, wherein the male-threaded fastener comprises a bolt.
 23. Thesystem of claim 20, wherein the fastener receiving portion comprises amale-threaded fastener receiver, and wherein the fastener comprises afemale-threaded fastener.
 24. The system of claim 20, wherein the borecomprises a base, and wherein the second portion of the tubularstructure is configured to extend downwardly into the bore until itcontacts the base of the bore.
 25. The system of claim 24, wherein thebore further comprises an aperture in the base, wherein the fastener isconfigured to extend through the aperture to mate with the fastenerreceiving portion.
 26. The system of claim 20, wherein the bore isconfigured to orient the shaft properly when the shaft assembly isconnected to the club head.
 27. The system of claim 20, furthercomprising a plurality of club heads, each of the plurality of clubheads comprising a bore.
 28. The system of claim 27, wherein thefastener is configured to allow the club head to be exchange with adiffernet one of the plurality of club heads.
 29. The system of claim28, wherein the different club head comprises a different center ofgravity relative to the first club head.
 30. The system of claim 20,further comprising a plurality of shaft assemblies.
 31. The system ofclaim 30, wherein the fastener allows the shaft assembly to be exchangewith a different one of the plurality of shaft assemblies.
 32. Thesystem of claim 20, wherein the club head comprises a recesssubstantially below the bore, the recess configured so that the fastenerwill not strike the ground when the shaft assembly is connected with theclub head.
 33. The system of claim 20, wherein the golf club head is awood type golf club head.
 34. The system of claim 20, wherein the golfclub head is an iron type golf club head.
 35. The system of claim 20,wherein the golf club head is a hybrid type golf club head